Excessive writes to backend

[fspmarshall]

When running tests for the 4.3 release (10k IoT nodes with DynamoDB backend), there were 2-4x more writes against the backend than I expected based on the number of nodes and the configured heartbeat interval. After noticing this, I tested the same scenario with the latest 4.2 and 4.1 releases and saw similar write numbers.

It could be that my estimates on the expected number of writes is just wrong, but its worth further investigation to make sure that we aren't producing excessive writes somewhere.

[fspmarshall]

Closing for being outdated. If we see this again we can create a new issue.